With social progress and economic development, everywhere we can see the situation where human beings have to face strong noise environment, e.g., when operating next to a large machine (such as loom lathes, air compressors, blowers, etc.) in the industrial production, presenting in roar of modern transports (such as motorcycles, trains, airplanes, etc.), and being in construction sites or military battlefields, and so on. Strong noise can cause a number of serious problems.
Firstly, the high-intensity noise may make people feel tired and produce negative emotions and seriously damage people's nervous system, blood circulatory system, endocrine system and digestive system as well as vision, hearing and intelligence. Therefore, hearing protection in a strong noise environment is an essential measurement. Secondly, in a strong noise environment, the speaker's voice signals may be completely submerged by ambient noises when using a headset for voice communication, so voice communication process cannot be properly achieved, which may lead to serious impact on production, life, military operations, etc and huge losses to individuals, organizations and even a country. As can be seen, it is significantly important to maintain a clear and stable voice communication function, which has also been a hot topic for researchers. Thirdly, in some strong noise environments, while people's hearing is protected, they also need to keep sensitive to the sound in the surrounding environment enough to monitor real time changes in the surrounding environment so as to make correct response, otherwise they may be unconscious of possible danger signals. For example, in a battlefield environment, the soldiers would apparently be in a very passive and dangerous situation if they cannot hear the ambient sound.